mfd: twl6040: Use regmap for register cache

Rather then open coding a cache of the vibra control registers use the
regmap cache code.  Also cache the interrupt mask register, providing
a small performance improvement for the interrupt code.

Signed-off-by: Mark Brown <broonie@linaro.org>
Acked-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

include/linux/mfd/twl6040.h

@@ -229,7 +229,6 @@ struct twl6040 {
 	int audpwron;
 	int power_count;
 	int rev;
-	u8 vibra_ctrl_cache[2];
 
 	/* PLL configuration */
 	int pll;